1. Field of the Invention
The present invention relates to a vane type hydraulic actuator for controlling the timing of opening and closing of an intake and/or exhaust valve, corresponding to an operational state of an engine.
2. Description of the Prior Art
FIG. 18 is a cross sectional view of a vane type hydraulic actuator invented by the inventors of this application and is disclosed in JP-9-314069-A. FIG. 19 is a detailed cross sectional view of the plunger part shown in FIG. 18. FIG. 20 is a cross sectional view of the plunger part in a state that a hydraulic pressure is applied.
Reference numeral 19 denotes an intake side cam shaft having an intake side cam 19a. An actuator 40 is connected to an end of the intake side cam shaft 19, and a timing pulley 21 is disposed around the actuator 40. The working oil of the actuator 40 is lubrication oil, delivered from an engine (not shown). The actuator is actuated by the working oil so as to adjust phase angle of the rotation of the intake side cam shaft 19 so that the opening and closing timings of intake valves of the engine can be continuously adjusted. The intake side cam shaft 41 is supported by a bearing 19. The actuator 40 has a housing 42, which can freely rotate around the intake side cam shaft 19.
A case 43 is fixed to the housing 42. And a vane type rotor 44 is received in the case 43. The vane rotor 44 is fixed to the intake side cam shaft 19 by means of bolts 45. The rotor 44 is rotatable relative to the case 43 in a predetermined anglular region.
The case 43 and the rotor 44 form hydraulic pressure chambers separated from each other. A chip seal 46 is disposed between the case 43 and the rotor 44 so that no oil leakage between the oil pressure chambers can occur. A back spring 47 made of an iron plate is disposed to push the chip seal 46 towards the rotor 44.
The housing 42, the case 43 and a cover 48 connected to the case 43 are fixed by a common volt 49. An O-ring 50 is disposed between the case 43 and the bolt 50. A plate 51 is fixed to the cover 48 by a bolt 52. Reference numerals 53, 54 denote O-rings. A cylindrical holder 55 is disposed in the rotor 44. The cylindrical holder 55 has an engaging hole 55a, which can engage with a plunger 56, as will be explained below.
The plunger 56 disposed in the housing 42 can slide therein and has an engaging shaft 56a, which can engage with the engaging hole 55a of the holder 55. The plunger 56 is pushed by a spring 57 towards the holder 55. Working oil is delivered into the engaging hole 55a of the holder 55 through a plunger oil channel 58. When working oil is delivered into the engaging hole 55a of the holder 55, the plunger 56 moves opposingly to the spring 57 so that the plunger 56 is unlocked from the holder 55. The rotor 44 is fixed to the intake side cam shaft 19 by means of a bolt 60. Reference numerals 59, 61 denote air holes.
A first and second oil channels 62, 63 are disposed in the intake side cam shaft 19 and the rotor 44. The first oil channel 62 communicates with an oil pressure chamber for timing retard 73, and the second oil channel 63 communicates with an oil pressure chamber for timing advance 74.
The amount of the working oil to be delivered to the actuator 40 is controlled by an oil control valve 80, which will be abbreviated to OCV hereinafter.
The OCV 80 comprises a valve housing 81, a spool 82 which can slide in the valve housing 81, a spring 83 urging the spool 82 toward one direction, and a linear solenoid 84 for displacing the spool 82 resisting the spring 83. The OCV is connected with an oil pan 91 through an oil supplying pipe 85a. An oil pump 92 and an oil filter 93 are disposed in the oil supplying pipe 85a. The first and second oil channels 62, 63 are connected with the OCV 80 through a first and second oil pipes 89, 90, respectively. The working oil returns to the oil pan 91 from the OCV 80 through an oil drain pipe 88. The oil pan 91, the oil pump 92, the oil filter 93 are a part of a lubrication system for lubricating portions to be lubricated in the engine (not shown), and simultaneously they form a working oil delivery system to the actuator 40.
An electronic control unit 100, which is abbreviated to ECU hereinafter, controls the amount of fuel injection into the engine, the timings of the ignition, and the timing of the opening and closing of valves. The control corresponds to the inputs from an intake air amount sensor, a throttle sensor, crank angle sensor and a cam angle sensor, which are not shown. The electronic control unit 100 further controls the closing timing of valves after the switching off of the ignition switch.
FIG. 21 is a cross sectional view of FIG. 18 along the line X--X. FIG. 22 shows a state in which a slide plate shown in FIG. 21 is displaced. FIG. 23 is a cross sectional view of FIG. 18 along the line Y--Y, FIG. 24 is a cross sectional view of FIG. 18 along the line Z--Z.
As shown in the figures, a first to fourth vanes 64-67 project radially from the rotor 44. A chip seal 68 is disposed at the tip of each vane 64-67. The chip seal 68 contacts with the inner surface of the case 43 and can slide along the surface. The chip seals 68 seal between the chambers disposed at both sides of the vanes. By the way, a back spring (not shown) is disposed behind each chip seals 68 for increasing the capacity of the sealing.
Four shoes 71 project inwardly from the inner surface of the case 43. The shoe 43 has a bolt hole 72, into which the bolt 49 shown in FIG. 18 is screwed.
The tip portion of each shoe 71 contacts with a vane supporting portion 69 of the rotor, namely the hub of the rotor, which supports the vanes. The tip portion of each shoe 71 slides along the outer surface of the vane supporting portion 69. Each room between the adjacent shoes 71 is divided by the corresponding shoe 71 into an oil pressure chamber for timing retard 73 and an oil pressure chamber for timing advance 74. These chambers 73, 74 are formed alternatively and have a form of a sector like room contoured peripherally by the inner surface of the case 43 and the outer surface of the rotor 44 and contoured radially by one of the shoes 71 and one of the vanes 64-67 of the rotor 44.
The oil pressure chamber for timing retard 73 is used for swing the first to fourth vanes 64-67 so that the timing of the opening and closing of valves is retarded. And the oil chamber for timing advance 74 is used for swing the first to fourth vanes 64-67 so that the timing of the opening and closing of valves is advanced.
The oil pressure chamber for timing retard 73 and the oil pressure chamber for timing advance 74 disposed at both side of the first vane 64 are communicated through a communicating channel 75, which passes through the first vane 64. A groove 76 is disposed in the communicating channel 75, and the plunger oil channel 58 communicates with the groove 76.
A slide plate 77 is disposed in the groove 76. The slide plate 77 divides the communicating channel 75 into two parts in such a manner that the oil leakage between the oil pressure chamber for timing retard 73 and the oil pressure chamber for timing advance 74 is prevented.
The slide plate 77 moves toward the oil pressure chamber for timing advance 74, when the oil pressure in the oil pressure chamber for timing retard 73 is higher. It moves towards the oil chamber for timing retard 73, when the pressure in the oil pressure chamber for timing advance 74 is higher. The arrow marks in FIGS. 21, 23, 24 show the rotation direction of the actuator 40 as a whole.
The oil pressure chambers for timing retard and advance 73, 74 are surrounded by the housing 42, case 43, rotor 44 and cover 48. The oil pressure chamber for timing retard 73 communicates with the first oil channel 62 so that working oil is delivered to the chamber 73 through the first oil channel 62. And the oil pressure chamber for timing advance 74 communicates with the second oil channel 63 so that working oil is delivered to the chamber 74 through the second oil channel 63. The rotor 44 rotates relatively to the housing 42, when the volumes of the oil pressure chambers 73, 74 change, corresponding to the amount of working oil delivered to each of the oil pressure chambers 73, 74.
The function of the actuator 40 and the OCV 80 is explained below.
At first, when the engine is stopping, the rotor 44 is positioned, as shown in FIG. 21, at the maximum timing advance position, namely, the rotor 44 has rotated at most in the timing advance direction. Also the oil pump 92 is stopping, therefore, no working oil is delivered either to the first and second oil channels 62, 63, as a result, no working oil is supplied to the plunger oil channel 58. Consequently, the oil pressure in the actuator 40 is low. As a result, the plunger 56 is pushed by the urging force of the spring 57 towards the holder 55 so that the engaging shaft 56a of the plunger 56 engages with the engaging hole 55a of the holder 55, that is to say, the rotor 44 is locked to the housing 42.
In this specification and Claims, a "timing advance direction" is a rotation direction of the rotor relative to the housing to advance the timing of the opening and closing of the valves, and a "timing retard direction" is a rotation direction of the rotor relative to the housing to retard the timing of the opening and closing of the valves.
Starting from this state, when the engine is started, the oil pump 92 functions to increase the oil pressure to the OCV 80 so that working oil is delivered through the first oil pipe 89 and the first oil channel 62 to the oil pressure chamber for timing retard 73 in the actuator 40. Due to the high oil pressure in the oil pressure chamber for timing retard 73, the slide plate 77 moves towards the oil pressure chamber for timing advance 74. As a result, the oil pressure chamber for timing retard 73 communicates with the plunger oil channel 58 so that the working oil is delivered through this plunger oil channel 58 into the engaging hole 55a of the holder 55. As a result, the plunger 56 is urged toward the spring, resisting the spring force, so that the engaging shaft 56a of the plunger 56 is pushed out from the engaging hole 55a of the holder 55a. That is to say, the engaging or locking between the plunger 56 and the rotor 44 is released.
Also in this state, due to the working oil delivered into the oil pressure chamber for timing retard, each vane 65-67 of the rotor 44 is pressed to a shoe 71 from the oil pressure chamber 73, and contacts with a flank of the shoe 71. Therefore, even in the unlocked state between the plunger 56 and the rotor 44, the housing 42 and the rotor 44 are pressing to each other due to the oil pressure in the oil pressure chamber for timing retard 73. As a result, the vibration or clashing in the actuator can be reduced or eliminated.
For changing the opening and closing timing of the valves, working oil is delivered from the OCV 80 to the oil chamber for timing advance 74 through the second oil pipe 90 and the second oil channel 63. The oil pressure in the oil chamber for timing advance 74 is delivered to the communicating channel 75 so that the slide plate 77 is pushed to move towards the oil pressure chamber for timing retard 73. Due to this movement of the slide plate 77, the plunger oil channel 58 communicates with the communicating channel 75 at the oil pressure chamber for timing advance 74 side so that the oil pressure in the oil pressure chamber for timing advance 74 is supplied to the plunger oil channel 58. Due to this high oil pressure, the plunger 56 moves towards the housing 42 resisting the force of the spring 57, so that the engaging or locking between the plunger 56 and the holder 55 is released.
In this unlocked state, the opening and closing of the OCV 80 is controlled so as to control the oil delivery to the oil pressure chambers for timing retard and advance 73, 74 so that the rotation angle of the rotor 44 relative to the rotation angle of the housing 42 is changed, that is to say, the rotor 44 is rotated in the timing advance direction or in the timing retard direction. For example, when the rotor 44 is rotated at most in the timing advance direction, the rotor rotates at a state that each vane 64-67 of the rotor 44 is contacting with a shoe 71 from the oil pressure chamber for timing retard 73 side, as shown in FIG. 22. When the oil pressure in the oil pressure chamber for timing retard 73 is higher than that in the oil pressure chamber for timing advance 74, the rotor 44 rotates in the timing retard direction relatively to the housing 42.
As explained above, the rotor 44 is controlled to rotate relatively to the housing 42 in the timing advance direction or in the timing retard direction, by adjusting the oil delivery to the oil pressure chambers for timing advance and retard 73, 74. The oil leakage at the oil delivery between the oil pressure chambers 73, 74 is prevented by means of chip seals 46, 68.
By the way, the oil pressure provided from the OCV 80 is controlled by the ECU 100, corresponding to the outputs from a position sensor, which detects the rotation angel of the rotor 44 relative to the housing 42, and a crank angle sensor, which determines the pressure to be supplied from the oil pump 92.
Another apparatus for adjusting the timings of the opening and closing of valves in an internal combustion engine using a vane type hydraulic actuator is disclosed in JP-9-60507-A, which employs a structure that one stopper pin, as a locking means, locks the rotor in the maximum timing retard position or in the maximum timing advance position, while the timings of the opening and closing of valves are adjusted at the starting of the engine.
As explained above, vane type actuators in the prior art employ a structure that one plunger 56 or one stopper pin, as a locking means, locks the rotor in the maximum timing retard position or in the maximum timing advance position, while the timings of the opening and closing of valves are adjusted at the starting of the engine.
In general, for optimizing the timings of opening and closing of valves in an intake/exhaust system of an engine, for example, the engine shall be started from a state, in which the rotor in the intake side is shifted a little from the maximum timing retard position towards the maximum timing advance position, and the rotor in the exhaust side is shifted a little from the maximum timing advance position towards the maximum timing retard position. As a result, the rotors in the intake side and the exhaust side have to be locked at an intermediate position. However, the locking at an intermediate position was difficult, when the structures of the vane type hydraulic actuators in the prior art are employed. The apparatus will be of more complex, when such structure in the prior art is modified to lock the rotors in an intermediate position. That is to say, the vane type hydraulic actuator in the prior art has the drawback that an optimization of timings of opening and closing of valves using a simplified structure was impossible.